This invention relates generally to the structure of shoes. More specifically, this invention relates to the structure of athletic shoes. Still more particularly, this invention relates to shoe soles that conform to the natural shape of the foot sole, including the bottom and the sides, when the foot sole deforms naturally during locomotion in order to provide a stable support base for the foot and ankle. Still more particularly, this invention relates to the use of deformation sipes such as slits or channels in the shoe sole to provide it with sufficient flexibility to parallel the frontal plane deformation of the foot sole, which creates a stable base that is wide and flat even when tilted sideways in natural pronation and supination motion.
The applicant has introduced into the art the use of sipes to provide natural deformation paralleling the human foot in pending U.S. application Ser. No. 07/424,509 now abandoned, filed Oct. 20, 1989, and as PCT Application No. PCT/US90/06028, which is comprised verbatim of the '509 application and was published as WO 91/05491 on May 2, 1991. It is the object of this invention to elaborate upon that earlier application to apply its general principles to other shoe sole structures, including those introduced in the applicant's other earlier applications.
By way of introduction, many conventional boat shoes are siped, a fairly archaic term derived from early automotive tire traction techniques which refers specifically to tread structure. As the term applies to shoes, siped shoe soles are provided with parallel slits or channels through portions of the shoe sole bottom, to increase traction for the otherwise typically smooth rubber sole bottom. This concept was originally introduced by Sperry with its old and famous "Topsider" boat shoe model, which incorporated U.S. Pat. Nos. 2,124,986, 2,206,860, and 2,284,307.
The traction sipes in the form of slits or channels run perpendicular to the long axis of the shoe, since slipping is most typical along that long axis coincident to locomotion forwards or backwards. The parallel traction slits typically penetrate to a depth of about a third or slightly more of the boat shoe.
The applicant's invention in the prior application Ser. No. 07/424,509 now abandoned is to use similar sipes such as slits or channels that, however, penetrate through most or even all of the shoe sole, to provide as much flexibility as possible to deform easily, rather than to increase traction. Moreover, the slits or channels of the applicant's prior invention are located on the opposite axis from those in conventional boat shoe soles.
Thus, the applicant's prior invention provides the shoe sole with flexibility roughly equivalent to the foot sole. Such flexibility will allow the shoe sole to parallel the frontal plane deformation of the human foot sole, which naturally creates a stable base that is wide and flat even when the foot is tilted sideways in either normal or extreme pronation and supination. In complete contrast, conventional shoes soles are extremely rigid in the frontal plane and become highly unstable when tilted sideways on their very narrow bottom sole edge.
The inherent instability of existing shoes is caused by a conventional shoe sole that will not deform to provide as much contact with the ground as the foot does naturally. Both conventional heel counters and motion control devices increase the rigidity of the shoe sole and therefore increase the stability problem, creating an unnaturally high and unnecessary level of ankle sprains and chronic overuse injuries.
The prior invention introduced sipes such as additional slits or channels on different axes to provide shoe sole motion paralleling the natural deformation of the moving foot in other planes. In addition, the prior invention provides flexibility to a shoe sole even when the material of which it is composed is relatively firm to provide good support. Without the invention, both firmness and flexibility would continue to be mutually exclusive and could not coexist in the same shoe sole; only a very soft material will allow a conventional shoe sole structure to deform naturally like the foot and such a sole would be highly unsatisfactory in terms of support, protection, and durability.
In addition to the prior pending application indicated above, the applicant has introduced into the art the concept of a theoretically ideal stability plane as a structural basis for shoe sole designs. That concept as implemented into shoes such as street shoes and athletic shoes is presented in pending U.S. applications Ser. No. 07/219,387, filed on Jul. 15, 1988, now U.S. Pat. No. 4,989,349, issued Feb. 5, 1991; Ser. No. 07/239,667, filed on Sep. 2, 1988, now U.S. Pat. No. 5,317,819, issued Jun. 7, 1994; Ser. No. 07/400,714, filed on Aug. 30, 1989 still pending; Ser. No. 07/416,478, filed on Oct. 3, 1989 still pending; Ser. No. 07/463,302, filed on Jan. 10, 1990 still pending; and Ser. No. 07/469,313, filed on Jan. 24, 1990 still pending, as well as in PCT Application No. PCT/US89/03076 filed on Jul. 14, 1989. PCT Application No. PCT/US89/03076, which is generally comprised of the virtually the entire '819 Patent verbatim (FIGS. 1-28) and major portions of the '349 Patent also verbatim (FIGS. 29-37), was published as International Publication Numbers WO 90/00358 on Jan. 25, 1990; PCT Application No. PCT/US90/04917, which is comprised verbatim of the '714 application, except for FIGS. 13-15 (which were published as FIGS. 38-40 of WO 90/00358), was published as WO 91/03180 on Mar. 21, 1991; PCT Application No. PCT/US90/05609, which is comprised verbatim of the '478 application, was published as WO 91/04683 on Apr. 18, 1991; PCT Application No. PCT/US91/00028, which is comprised verbatim of the '302 application, was published as WO 91/10377 on Jul. 25, 1991; PCT Application No. PCT/US91/00374, which is comprised verbatim of the '313 application, was published as WO 91/11124 on Aug. 8, 1991. The purpose of the theoretically ideal stability plane as described in these applications was primarily to provide a neutral design that allows for natural foot and ankle biomechanics as close as possible to that between the foot and the ground, and to avoid the serious interference with natural foot and ankle biomechanics inherent in existing shoes.
The applicant's prior application on the sipe invention and the elaborations in this application are modifications of the inventions disclosed and claimed in the earlier applications and develop the application of the concept of the theoretically ideal stability plane to other shoe structures. The theoretically ideal stability plane 51 is defined as the plane of the surface of the bottom of the shoe sole 31, wherein the shoe sole conforms to the natural shape of the foot, particularly the sides, and has a constant thickness in frontal plane cross sections. Accordingly, it is a general object of the new invention to elaborate upon the application of the principle of the theoretically ideal stability plane to other shoe structures.
It is an overall objective of this application to show additional forms and variations of the general deformation sipes invention disclosed in the '509 application, particularly showing its incorporation into the other inventions disclosed in the applicant's other applications. It is another objective of the invention to provide flexibility to a shoe sole even when the material of which it is composed is relatively firm to provide good support: without the invention, both firmness and flexibility would continue to be mutually exclusive and could not coexist in the same shoe sole.
These and other objects of the invention will become apparent from a detailed description of the invention which follows taken with the accompanying drawings.